Fix Configuration Handling

[DakotaNelson]

Right now, configuration is handled in two places: a .env file, which is used by Heroku, and the Flask configuration handling system.

This means that some parts of the application use os.environ.get, while others use current_app.config. This is confusing and bad, and leaves configuration scattered across multiple sources.

Solution:

Set up a default_settings.py file (perhaps give it a better name) that resembles this example, then update the configuration import in Flask (again, following this example), and make sure that everywhere in the code that uses os.environ.get is changed to use current_app.config. Ensure that all settings and configuration are handled in one place.